Stabilized organic material



United States Patent 3,530,069 STABILIZED ORGANIC MATERIAL James D.ONeill, Southfield, Mich., assignor to Ethyl Corporation, New York,N.Y., a corporation of Virginia No Drawing. Continuation-impart ofapplication Ser. No. 603,716, Dec. 22, 1966. This application Mar. 10,1969, Ser. No. 805,808

Int. Cl. ClOm 1/12, 3/32 US. Cl. 252-46.4 11 Claims ABSTRACT OF THEDISCLOSURE The combination of a dihydrocarbyl tin sulfide (e.g.,di-n-butyl tin sulfide) with a phenolic antioxidant exhibits asynergistic stabilizing efiect, especially in lubricating oils.Representative phenolic antioxidants are 4,4-bis- (2,6di-tert-butylphenol), 4,4'-thiobis(6-tert-butyl-rnetacresol),4,4-methylene bis (2,6-di-tert-butylphenol), and 2,2-methylene bis(4-methyl-6-tert-butylphenol) This application is a continuation-impartof application Ser. No. 603,716, filed Dec. 22, 1966, now U.S. 3,442,-806, issued May 6-, 1969.

This invention relates to the stabilization of organic material with thecombination of a dihydrocarbyl tin sulfide and a hindered phenolicantioxidant.

Hindered phenolic antioxidants are known to stabilize organic materials.For example, the stabilization of organic material with 4,4-methylenebis(2,6-di-tertbutyl phenol) is disclosed in US. 3,043,775, issued July10, 1962. Other phenolic stabilizers are disclosed in US. 3,069,384,issued Dec. 18, 1962, and U.S. 2,364,338, issued Dec. 5, 1944:Furthermore dialkyl tin sulfides are disclosed as anti-wear agents andstabilizers in lubricating oils in US. 3,077,451, issued Feb. 12, 1963.It has now been found that when the combination of a hindered phenolicantioxidant and a dihydrocarbyl tin sulfide is employed a degree ofstabilization is obtained which is totally unexpected from the amountobtained with either material by itself.

An object of this invention is to provide an improved means ofstabilizing organic material. A further object is to provide alubricating oil of improved stability. A still further object is toprovide a lubricating oil of good thermal stability.

These and other objects are accomplished by providing a synergisticstabilizer which comprises:

(A) From 199 weight percent of a tin compound having the formula:

(I) wherein R and R are independently selected from the group consistingof alkyl radicals containing 1-12 carbon atoms, cycloalkyl radicalscontaining 6-12 carbon atoms, aralkyl radicals containing 7-12 carbonatoms and aryl radicals containing 6-12 carbon atoms; and

(B) From 1-99 weight percent of a compound selected from the groupconsisting of (1) Compounds having the formula:

on (IJH 3,530,069 Patented Sept. 22, 1970 wherein R and R are selectedfrom the group consisting of alpha-branched alkyl radicals containing3-20 carbon atoms, alpha-branched aralkyl radicals contining 7-20 carbonatoms, cycloalkyl radicals containing 6-20 carbon atoms; R and R areselected from the group consisting of hydrogen, alkyl radicalscontaining 1-20 carbon atoms, cycloalkyl radicals containing 620 carbonatoms, and aralkyl radicals containing 7-20 carbon atoms, and Z is adivalent linking radical selected from the group consisting of sulfideradicals having the formula:

wherein n is an integer from 1-3, alkylidene radicals containing 2-12carbon atoms and alkylene radicals contain ing 1-12 carbon atoms;

(2) Compounds having the formula:

(III) wherein R R and R are selected from the same groups previouslydefined for these radicals;

(3) Compounds having the formula:

OH OH & CH CH2 5 0 R10 Ra wherein R R R and R are selected from the samegroups previously defined for these radicals, and R R R and R areselected from the group consisting of hydrogen, the hydroxyl radical,alkyl radicals containing from 1-6 carbon atoms, radicals having theformula:

wherein R is selected from the group consisting of alkyl radicalscontaining from 1-6 carbon atoms; radicals having the formula:

wherein R is selected from the group consisting of alkyl radicalscontaining from 1-6 carbon atoms, aryl radicals containing from 612carbon atoms, and aralkyl radicals containing from 7-18 carbon atoms;and radicals having the formula:

wherein R and R are selected from the same groups previously defined forthese radicals;

(4) Compounds having the formula:

(l)H OH Rs R4 wherein n is an integer from 1*3, and R R R and R areselected from the same groups previously defined for these radicals;

(5) Compounds having the formula:

wherein R and R are selected from the same groups previously defined forthese radicals;

(6) Compounds having the formula:

OII

(VII) wherein R R R and R are selected from the same groups previouslydefined for these radicals; and

(7) Compounds having the formula:

R5 p (Y III) wherein R and R are selected from the same groupspreviously defined for these radicals, R is a divalent hydrocarbonradical containing from 1 to about 3 carbon atoms, R is a hydrocarbonradical containing from 1 to about 20 carbon atoms and having thevalence p, p is an integer from 1-4, and q is an integer from 0-1.

Examples of tin compounds having Formula I are di-nbutyl tin sulfide,di-n-propyl tin sulfide, diisopropyl tin sulfide, di-n-pentyl tinsulfide, di-n-hexyl tin sulfide, npropyl-n-hexyl tin sulfide,2-sec-pentyl-isopropyl tin sulfide, dimethyl tin sulfide, di-n-dodecyltin sulfide, dicyclohexyl tin sulfide, cyclohexyl-n-butyl tin sulfide,di(3,5- dimethylcyclohexyl) tin sulfide, dibenzyl tin sulfide, di-(a-methylbenzyl) tin sulfide, di(4-tert-butylbenzyl) tin sulfide,diphenyl tin sulfide, di(3,5-diisopropylphenyl) tin sufide, and thelike.

Some representative examples of phenolic compounds having Formula II are4,4'-methylene bis 2,6-diisopropylphenol 2,2-ethylidenebis(4,6-di-tert-octylphenol),

4,4-butylidene bis(6-tertbutyl-meta-cresol) 4,4-( l-methyl-propylidene-bis- (Z-tert-butylJ-methylphenol),

4,4'-isopropylidene bis(2,6-di-tert-butylphenol),

4,4'-isopropylidene bis[2,6-di(a-methylbenzyl)phenol],

4,4'-methylene bis[2-tert-butyl-6-(q-methylbenzyl) phenol],

4 2,2'- l-methyl-pentylidene) -bis-(Z-tert-butyl-l-methylphenol),2,2-methylene bis(4methyl-6-tertbutylphenol), 4,4'-benzylidenebis(2,6di-tert-butylphenol), 4,4-methylene bis(2,6-di-tert-butylphenol),4,4'-( l-methyl-3-carboxypropylidene)-bis-(2,6-di-tertbutylphenol),4,4-cyclohexylidene bis(2,6-dicyclohexylphenol), 4,4-cyclohexylidenebis(2,6-di-tert-butylphenol), 4,4-ethylidenebis(2,6-di-tert-butylphenol), 4,4.-(l-methylethylene)-bis-(2,6-diisopropylphenol),4,4'tetra-methylene-bis(2-methyl-6'tert-butylphenol) 2,2'-decamethylenebis(4-methyl-6-tert-butylphenol), 4,4-thiobis(6-tert-butyl-meta-cresol),4,4'-thiobis 2-meth yl-6-tert-butylphenol) 4,4'-thiobis-2,6-di-tert-butylphenol) 2.2-dithiobis(4,6-di-tert-butylphenol),4,4-thiobis[2,6-di(ot-methylbenzyDphenol],4,4'-thiobis(2,6-dicyclohexylphenol),4,4-trithiobis(Z-methyl-6-cyclohexylphenol), 4,4-dithiobis[2-methyl-6-(a,a-dimethylbenzyl) phenol]2,2-thiobis(4-methyl-6-tert-butylphenol), and the like.

Some examples of phenolic compounds having Formula III are2,6-di-tert-butylphenol, 2,4,6-tri-tert-butylphenol,2,6-di-tert-butyl-4-methylphenol, o-tert-butylphenol,2,6-dicyclohexylphenol, 2,6-dicyclohexyl-4-methylphenol,2-methyl-6-tert-butylphenol, 2,6-di(ot-methylbenzyl)phenol,2,4-di(a,a-dimethylbenzyl)phenol, 2,4-di-tert-octylphenol,2,4,6-tri(a-methylbenzynphenol, o-sec-eicosylphenol,2-(2-sec-dodecyl)-4-methylphenol, and the like.

Examples of compounds having Formula IV are 2,4,6-tri- 3 ,5-di-tert-butyl-4-hydroxybenzyl phenol,

1,3 ,5 -tri-methyl-2,4,6-tri 3,5 -ditert-butyl-4-hydroxybenzyl benzene,

2,6-di 3 ,5 -di-tert-butyl-4-hydr0xybenzyl -4-tert-butylphenol,

2,4-di 3-tert-butyl-4-hydroxy-5- 2-sec-dodecyl benzyl] phenyl acetate,

2,6-di(3,S-di-tert-butyl-4-hydroxybenzyl) -4-tert-butylphenylpropionate,

2,6-di (3 ,5 -di-tert-butyl-4-hydroxybenzyl) -4-tert-butylanisole,

1,2,4,5-tetramethyl-3 ,6-di 3 ,5 -di-tert-butyl-4-hydroxybenzyl benzene,

2, 6-di- 2-hydroxy-3 -tert-butyl-5-methylbenzyl -4-methyl hexoxybenzene,

1,3 ,S-tri 3 ,S-di-tert-butyl-4-hydroxybenzyl benzene, and

the like.

Representative examples of phenolic compounds having Formula V includea,ot-thiobis( 2,6-di-tert-butyl-p-cresol) a,a-thiobis[2,6-di(tx-methylbenzyD-p-cresol] oc,ct'- [4-tert-octyl-6-(a,a-dimethylbenzyl) -p-cres0l] a,vt'-dithiobis2-methyl-6-sec-butyl-p-cresol), ot,zx'-thl0bl$2,6-dicyclohexyl-p-cresol),

' a,ot'-trithiobis(2-tert-butyl-4-methyl-0-cresol), and the like.

Examples of phenolic compounds having Formula VI are2,6-di-tert-butyl-tx-dimethylamino-p-cresol, 2,4,6-tris( 3,5-di-tert-butyl-4-hydroxybenzyl) amine,3,5-dicyclohexyl-4-hydroxybenzyl-dimethylamine, N,N-di 3 ,5-di-tert-butyl-4-hydroxybenzyl phenylamine, N-3,5-dicyclohexyl-4-hydroxybenzyl -N-methylaniline- N-phenylamine,

Z-tert-dodecyl-4-methyl-a-dibenzylamino-o-cresol, and

the like.

Some representative examples of the phenolic compounds represented byFormula VII are 4,4-bis 2,6-di-tert-butyl phenol) 4,4'-bis2,6-dicyclohexylphenol 4,4'-bis 2-methyl--tert-octylphenol 2,2-bis4-methyl-6-tert-butylphenol 4,4'-bis [2,6-di-(u-methylbenzyl)phenol] andthe like.

Examples of compounds having Formula VIII includepentaerythritol-tetrakis- 3,3,5-di-tert-butyl-4-hydroxyphenyl-propionate],

pentaerythritol-tetrakis-3,5-di-tert-butyl-4-hydroxybenzoate,

ethylene glycol bis 3- 3 ,5 -di-tert-butyl-4-hydroxyphenyl propionate]hydroquinone bis 2- 3 ,5 -di-tert-butyl-4-hydroxyphenyl) acetate] methyl3-methyl-5-tert-butyl-4-hydroxybenzoate,

pentaerythritol-tetrakis 3- 3-tert-butyl-5-methyl-4- hydroxyphenyl-propionate] lauryl 3,5 -dia-methylbenzyl) -4-hydroxybenzoate,

glycerine tris 3- 2-hydroxy-3-tert-b utyl-4-methylphenyl)-propionate]and the like.

Of the foregoing, the preferred synergist combination is represented bythe combination of the tin compounds of Formula I and the phenoliccompounds of Formula II. Of these, the more preferred combinations arerepresented by the combination of di-butyl tin sulfide with at least oneof the folowing phenolic compounds:

4,4'-thiobis 2,6-di-tert-butylphenol) 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-thiobis Z-methyl-6-tert-butyl-phenol)4,4-thiobis 6-tert-butyl-meta-cresol and 2,2-thiobis- 4-methylG-tert-butylphenol) Of the foregoing, the most preferred combinationsare represented by the combination of di-butyl tin sulfide with4,4-thiobis(2,6-di-tert-butylphenol) and the combination of di-butyl tinsulfide with 4,4'-methylenebis(2,6-ditert-butylphenol) The synergisticcombinations are effective stabilizers of organic material. By the termorganic material is meant those organic materials normally tending toundergo oxidative and thermal degradation. Examples of such materialsinclude plastics, liquid hydrocarbon fuels, lubricants, functionalfluids and rubber.

In this invention the term plastic is used to represent any one of agroup of materials which consist of, or contains as an essentialingredient, a thermosetting or thermoplastic substance of high molecularweight, and which, while solid in the finished state, at some stage inits manufacture is soft enough to be formed into various shapes usuallythrough the application, singularly or together, of heat and pressure.Examples of such plastics are the phenolic resins; the aminos, such asunreaformaldehyde resins and melamine-formaldehyde resins; theunsaturated and saturated polyester resins, including the oil modifiedalkyd resins; the styrene homo-polyrners and co-polymers, such aspolystyrene and styrene-acrylonitrile co-polymers; the acrylic monomersand polymers; substituted acrylic and methacrylic acids, their salts,esters, and other derivatives, such as nitriles and amides; thecellulosics, such as cellulose acetate, cellulose acetate butyrate,cellulose nitrate, cellulose propionate, ethyl cellulose,nitrocellulose, carboxymethyl cellulose, hydroxyethyl cellulose, andcellophane; linear and branched polyolefins, such as polyethylene andpolypropylene; the polyurethanes; the vinyl homopolymers andco-polymers, such as polyvinyl chloride, polyvinyl acetate, polyvinylchloride acetate, polyvinyl acetate, polyvinyl alcohols, polyvinylbutyral, and polyvinyl formal, polyvinylidene chloride, polyvinylideneco-polymers, polyvinyl alkylethers, polyvinyl pyrrolidene, polyvinylcarbazole, polyvinyl naphthenate, polyvinyl benzoate, and polyvinylfluoride; the polyamides; and the condensation products of diabasicorganic acids and diamines such as nylon.

The above material also includes those plastics which are in combinationwith other material, for example, with fillers such as flour, cotton,shredded or chopped cloth, chopped canvas, paper pulp forms, asbestos,powdered mica, calcium carbonate, carbon, graphite, quartz, diatomaceoussilica, fibraus glass, barytas, calcium silicate, iron, barium sulfate,litharge and clay; plasticizers such as phthalates, phosphates, estersincluding adipates, azelates and sebacates, polymeric plasticizersincluding polyesters of adipic, azelaic, and sebacic acid with glycolsterminated with long-chain fatty acids, epoxy, fatty acid esters, estersof glycols such as phthalyl glycolates, sulfonamides; secondaryplasticizers including hydro-carbons, chlorinated hydrocarbons andnitrated hydrocarbons; polymerizable plasticizers; stabilizers such asinorganic acid derivatives including basic lead carbonate, tribasicleadsulfate, dibasiclead phosphite, sodium carbonate, di-, and trisodiumphosphate and the salts of polyphosphoric acid partial esters, organicacid salts including the metal salts of stearic, lauric, ricinoleic,capric, caproic, myristic, Z-ethylhexanoic, maleic, phthalic,naphthenic, a-lkylated benzoic and salicylic acids, organometallicsincluding dibutyltin dilaurate, dibutyltin maleate and their mixtures,dibutyltin monomethoxy, monomethylmaleate and the dialkyltin mercaptans,organic compounds including the epoxides, polyols, nitrogen derivatives;antioxidants; colorants such as the dyes, the organic pigments andinorganic pigments; and reinforcing fibers.

The additives of this invention can be incorporated into the plasticmaterial by a variety of means. For example, a convenient method ofaddition to plasticized materials is to dissolve the stabilizer in theplasticizer. The stabilizer can also be added by dry blending with theresin powder or granules prior to processing. For example, withpolyesters, the stabilizer can be added to the resin from a master batchsolution of the stabilizer in the monomer, or they can be incorporatedby stirring into the cut polyester resin system; in polystyrene aconvenient procedure is to add these materials to the polystyrene beads.The mixture is then dry-tumbled and extruded. With cellulosics,incorporating the stabilizer in the plasticizer is very convenient. Invinyl plastics the stabilizer may be added to a dry powder form of therigid vinyl co-polymer. The mixture is then milled and calendered orextruded. In polyethylene the stabilizer can be added to the raw polymerat the same time as other ingredients. The resultant mixture is thensubjected to extrusion or calendering. The stabilizer can also be addedto dry polyethylene and mixed by milling. In plastics containing fillersof the various sorts, the stabilizer can be premixed with the fillerbefore its incorporation.

In order to stabilize the organic material all that is required is thata stabilizing quantity of the additive composition be added to theorganic material. It is our intention not to limit our invention to anyparticular concentration range, inasmuch as the concentration ofadditive required for any particular application can be quite differentfrom that required for another application. However, we have found that,in most cases, a concentration of up to about 5 percent of the additivecompound in the organic material gives satisfactory results. A preferredrange is from 0.001 to about 3 percent by Weight of the additivecompound in the organic material. I have found this preferred range togive excellent results in most embodiments of my invention.

The following examples illustrate the stabilized organic compositions ofthis invention. All parts are parts by weight unless otherwiseindicated.

2? EXAMPLE 1 Five weight percent of a stabilizer comprising 10 weightpercent of di-n-butyl tin sulfide and 90 weight percent of4,4'-methylene bis(2,6-di-tert butylphenol) is mixed with the dibutylester of phthalic acid. This solution is sprayed onto powdered celluloseacetate. The mixture is heated, blended and poured into a mold cavitywherein it is extruded into a sheet.

EXAMPLE 2 Two-hundredths weight percent of a stabilizer comprising 1weight percent of di-phenyl tin sulfide and 99 weight percent of4,4-thiobis(2,6-di-tertbutylphenol) is added to dry powdery polyvinylacetate. The mixture is then milled and extruded into sheets, yielding astable plastic.

EXAMPLE 3 Polyester resin is cut finely and stirred in a heated vessel.0.08 weight percent of a stabilizer comprising 50 weight percentdi-cyclohexyl tin sulfide and 50 weight percent of 2,2-methylenebis(4-methyl 6-tert-butylphenol) is added and the mixture is heated,poured into a mold and extruded into a sheet, yielding a highly stablepolyester plastic.

EXAMPLE 4 One weight percent of a stabilizer comprising 5 weight percentof n-butyl-isopropyl tin sulfide and 95 weight percent ofa,a'-thiobis(6-tert-butyl-rn-cresol) is added to polystyrene beads. Themixture is thoroughly mixed, poured into a mold and extruded intosheets, yielding a polystyrene plastic of enhanced thermal and oxidativestability.

EXAMPLE 5 Methyl methacrylate is mixed with 0.001 weight percent of astabilizer comprising 99 weight percent of diamyl tin sulfide and 1weight percent of 1,3,5-tri-methyl- 2,4,6 tri(3,5 di tert butyl 4hydroxybenzyl)benzene. It is then poured into a mold and extruded underheat and pressure into a thin sheet.

EXAMPLE 6 Three weight percent of a stabilizer comprising 25 weightpercent of di-phenyl tin sulfide and 75 weight percent of2,6-di-tert-butyl-p-cresol is mixed with dry powdered half-secondbutyrate plastic, poured into a mold and extruded with heat and pressureinto a thin sheet of great stability.

EXAMPLE 7 A linear polyethylene having a high degree of crystallinity,up to 93 percent, and less than one ethyl-branched chain per 100 carbonatoms, a density of about 0.96 and which has about 1.5 double bonds per100 carbon atoms is treated with 50X 10 roentgens of ,8 radiation. Tothe thus irradiated polymer is added 0.001 percent of a stabilizercomprising 75 weight percent of dilauryl tin sulfide and 25 weightpercent of 4,4'-thiobis(2-methyl-6-tertbutylphenol), yielding a highlystable organic plastic.

EXAMPLE 9 Two parts of a stabilizer comprising weight percent ofdi-methyl tin sulfide and 85 weight percent of 2,4,6- tri(3,5 di tertbutyl 4 hydroxybenzyl)phenol are added with milling to 100 parts of alow density polyethylene which has a specific gravity of 0.910, acompression ratio of 1.8, a tensile strength of 1000 p.s.i., a Shore Dhardness of 41 and a heat distortion temperature under 66 p.s.i. of 105C. The resulting product is vastly improved in its stability towards thedeleterious effects of heat.

EXAMPLE 10 To 10,000 parts of a medium density polyethylene having aspecific gravity of 0.933, a compression ratio of 2.0, a tensilestrength of 1800 p.s.i., a Shore D hardness of 60 and a heat distortiontemperature under 66 p.s.i. of 135 F. is added 10 parts of a stabilizercomprising 1 percent of di-n-butyl tin sulfide and 99 weight percent of2,6-ditert-butylphenol, yielding a highly stable polyethylene plastic.

EXAMPLE 11 To a batch of polypropylene having a specific gravity of 0.9,a tensile strength of 4300 p.s.i., a compression strength of 8500p.s.i., a Rockwell hardness of and a heat distortion temperature under66 p.s.i. of 210 F. is added 3 weight percent of a stabilizer comprising10 weight percent of di-n-butyl tin sulfide and Weight percent of 06,06-thiobis(2,6-di-tert-butyl-p-cresol), resulting in a polypropyleneplastic of enhanced stability.

EXAMPLE 12 To a polypropylene having a specific gravity of 0.91, a heatdistortion temperature of 230 F., a Rockwell hardness of 110, a tensilestrength of 5700 p.s.i. and a compression strength of 10,000 p.s.i. isadded 0.5 weight percent of a stabilizer comprising 20 weight percent ofdi-nbutyl tin sulfide and 80 weight percent of pentaerythritoltetrakis[3 (3,5 di tert butyl 4 hydroxyphenyl)propionate], resulting ina product having excellent stability towards the deteriorative effectsof heat and oxygen.

EXAMPLE 13 To 5000 parts of a Ziegler type polypropylene is added 10parts of a stabilizer comprising 10 Weight percent of di-n-butyl tinsulfide and 90 weight percent of 4,4-methylenebis(2,6-di-tert-butylphenol), yielding a plastic of excellent stability.

EXAMPLE 14 To 20,000 parts of polytetrafiuoroethylene molding compoundhaving a density of 2.22, a tensile strength of 4500 p.s.i., acompression strength of 1700 p.s.i., a Shore D hardness of 65 and a heatdistortion temperature of 250 F. is added 10 parts of a stabilizercomprising 50 weight percent of di-benzyl tin sulfide and 50 weightpercent of 3,S di-tert-butyl-4-hydroxybenzyl sulfide, yielding a stableorganic material.

EXAMPLE 15 To a vinyl acetate molding compound having a specific gravityof 1.18, a tensile strength of 5000 p.s.i., and a heat distortiontemperature of F. is added 0.5 weight percent of a stabilizer comprising75 weight percent of diisopropyl tin sulfide and 25 weight percent of2,6-di-tertbutyl-ot-dimethylamino-p-cresol, yielding a highly stablepolyvinyl acetate.

EXAMPLE 16 To 100 parts of polyvinylchloride molding compound having aspecific gravity of 1.45, a compression ratio of 2.4, a tensile strengthof 9000 p.s.i., a compression strength of 13,000 p.s.i., a Shore Dhardness of 90 and a heat distortion temperature of F. is added one partof a stabilizer comprising 30 weight percent of di-nbutyl tin sulfideand 70 weight percent of 4,4-bis(2,6-di-tert-butylphlenol), yielding apolyvinyl chloride of increased stabi ity.

9 EXAMPLE 17 To 5000 parts of polychlorotrifluoroethylene having adensity of 2.1, a compression ratio of 2.0, a tensile strength of 5700p.s.i., a compression strength of 32,000 p.s.i. and a Rockwell hardnessof 110 is added 10 parts of a stabilizer comprising 13 weight percent ofdi-sec-butyl tin sulfide and 87 Weight percent of 2,2-thiobis(4-methyl-6-tert-butylphenol), yielding an organic plastic of enhanced stability.

The stabilizers of this invention are also very effective antioxidantsfor rubber materials such as polybutadiene, methyl rubber,polyisopropene rubber, polybutene rubber, styrene-isoprene rubber,natural rubber, butyl rubber, SBR rubber, GR-N rubber,isobutylene-isoprene rubber, piperylene rubber, ABS rubber,dimethylbutadiene rubber, poly-cis-butadiene rubber, styrene-chloroprenerubber, and the like. Thus, a preferred embodiment of the presentinvention is a rubber containing as an antioxidant therefor asynergistic stabilizer comprising a dihydrocarbyl tin sulfide and aphenolic compound selected from the classes previously defined. Thestabilizer is incorporated into the hubber by milling. Banbury mixing,or similar process, or is emulsified and the emulsions added to therubber latex before coagulation. In the various embodiments of thisinvention the stabilizer is used in small antioxidant amounts, generallyranging from about 0.001 to about 3.0 percent, based on the rubber.

As used in the description and claims, the term rubher is employed in ageneric sense to define a high molecular weight plastic material whichpossesses high extensibility under load coupled with the property offorcibly retracting to approximately its original size and shape afterthe load is removed. It is preferable that the rubber be asulfur-vulcanizable rubber, such as India rubber, reclaimed rubber,balata, gutta percha, rubbery conjugated diene polymers and copolymersexemplified by the butadiene-styrene (SBR), butadiene-acrylonitrile(GR-N or Paracril) rubbers, polyisoprene, poly-cis-butadiene, and thelike, although the invention is applicable to the stabilization of anyrubbery, high molecular weight organic material which is normallysusceptible to deterioration in the presence of oxygen, air, or ozone.The nature of these rubbers is well known to those skilled in the art.

The rubber compositions of the present invention are illustrated by thefollowing specific examples, wherein all parts and percentages are byweight.

EXAMPLE 18 To illustrate the enhanced oxygen resistance of the rubbercompositions of this invention a light-colored stock is selected fortest. This stock had the following composition:

Parts by weight Pale crepe rubber 100.00

To the above base formula is added one part by weight of a stabilizercomprising 1 percent of di-n-butyl tin sulfide and 99 percent of4,4-methylene bis(2,6-di-tertbutylphenol). Individual samples are curedfor 30 minutes at 274 F. using perfectly clean molds with no moldlubricant. The resulting vulcanized natural rubber is resistant tooxidative degradation.

1 0 EXAMPLE 19 EXAMPLE 20 SBR rubber is compounded according to thefollowing formula:

Parts SBR latex (S/B ratio 29/71) 100 Wax 2 Ultramarine dye 0.1 Zincoxide Titanium dioxide 20 Sulfur 3 Stearic acid 1.2

Mixture of 25% di-phenyl tin sulfide and 2,6-

di-tert-butylphenol Benzothiazyl disulfide 0.4 Amine activator 0.5

This stock is mixed in a Banbury blender and then vulcanized for 60minutes at 280 F.

EXAMPLE 21 A butadiene-acrylonitrile copolymer is produced frombutadiene-l,3 and 32 percent of acrylonitrile. Two percent (based on thedry weight of the copolymer) of a stabilizer comprising 50 weightpercent of di-benzy1 tin sulfide and 50 weight percent of 2,2'-methylenebis(4-methyl-6-tert butylphenol) is added as an emulsion in sodiumoleate solution to the latex obtained from emulsion copolymerization ofthe monomers. The latex is coagulated with a pure grade of aluminumsulfate and the coagulum, after Washing, is dried for 20 hours at 70 C.The latex is then ready for further compounding and vulcanization.

The stabilizers are eminently useful for stabilizing lubricants. Forexample, they improve the stability of mineral oils and greases;silicon-containing oils and greases including the siloxanes, silanes,and silicate esters; fluorocarbon oils and greases; diester oils andgreases, aromatic ether oils and greases; phosphate ester oils andgreases; polyalkylene glycol oils and greases; synthetic hydrocarbonoils and greases formed from polybutene oils and other low molecularweight polyolefin oils and tetrahydrofuran polymer oils and greases.

The minerals oils and greases include hydrocarbon oils and greasesobtained through conventional refining processes of the petroleum crudestocks. Such conventional refining processes include distillation,solvent extraction, clay filtration, dewaxing, acid treatment andpropane deasphalting. The constituents of mineral oils and greases maybe summarized as (1) straight chain parafiins, (2) branched chainparafiins, (3) naphthenes, (4) aromatics and (5) mixedaromatic-naphtheneparaflin.

The silicon-containing oils and greases include the polysiloxane oilsand greases of the type, polyalkyl, polyaryl, polyalkoxy, andpolyaryloxy such as the polymethyl siloxane, polymethylphenol siloxaneand polymethoxyphenoxy siloxane. Further included are silicate esteroils, such as the tetraalkyl and tetraaryl silicates of thetetra-Z-ethylhexyl and tetra-p-tert-butylphenyl types and the silanessuch as the mono-, di-, and trisilanes. Also included are thechlorinated siloxanes such as the chlorophenyl siloxanes, andchloroalkyl siloxanes. Examples of typical silanes are diethyldihexylsilane, dibutyl diheptylsilane, diphenyl diethylsilane andbis(ndodecyl)dichlorosilane and bis(n-dodecyl dioctyl)-silane.

The fluorocarbons are compounds which contain carbon and fluorinne. Thisclass of compounds is analogous structurally to the hydrocarbons. Thus,the compounds are generally linear polymers built up of a recurring unitwhich is As used in the specification the term fluorocarbon is meant toinclude compounds which can also contain chlorine and hydrogen. Suchcompounds are linear polymers built up from a recurring unit such as inwhich at least one X is fluorine and the other Xs are chlorine, fluorineor hydrogen. Thus, the fluorocarbon can be polytetrafluoroethylene,polymonochloridifluoroethylene, polymonochloromonofluoroethylene and thelike.

The polyester oils and greases are esters formed by the reaction betweenpolybasic acids and alcohols or monobasic acids and glycols. Thediesters of branched chain aliphatic alcohols and straight chain dibasicacids have been found to be the most desirable polyesters forlubricating purposes. The synthetic polyesters have high viscosityindices, high flash points and exceptionally low pour points as comparedto petroleum oils of similar viscosity and have found use chiefly asaircraft instrument oils, hydraulic and damping fluids and precisionbearing lubricants wherein their exceptionally low temperature fluidityproperties are particularly suited. Typical examples of such esters arediisooctyl azelate, di(2-ethylhexyl)sebacate, di-sec-amyl sebacate,diisooctyl adipate, di(2-ethylhexyl)adipate, di(2-ethylhexyl-azelate,di(l-methyl-4-ethyloctyl)glutarate, di-isoamyl adipate, di(2ethylhexyl(glutarate, di(2 ethylbutly)adipate, ditetradecylsebacate anddi(2-ethylhexyl)pinate.

The polyalkylene glycol oils and greases are composed of long chainlinear polymers which are generally formed from the reaction of analiphatic alcohol and an epoxide such as ethylene or propylene oxide.The products of such a reaction are complex and thus polyalkylene glycollubricants may contain the ethers and esters of polyethylene andpolypropylene glycol. (Also included within this terminology are thereaction products formed from higher polyalkylene oxides, polyglycidylethers and polythioglycols.)

These substances are manufactured and marketed in considerablequantities under the trade name Ucon. They are useful lubricants becauseof their flat viscositytemperature curves, their low viscosity in thesubzero temperature range as well as their low freezing points. Theygenerally have viscosities at 100 F. ranging from 135 to 1200 SayboltUniversal seconds, flash points ranging from 300 to 500 F. and specificgravities ranging from about 0.97 to about 1.01.

T etarahydrofuran polymer oils and greases are formed by thecopolymerization of tetrahydrofuran and an alkylene oxide such asethylene oxide. In the polymerization reaction the furan rings areruptured forming straight chain tetrahydrofuran polymers to which theethylene oxide groups are probably attached as side chains.

Polybutene lubricants are formed from the polymerization of isobutene.Isobutene, usually containing also some normal butene, is polymerized atlow temperatures in the presence of a catalyst such as aluminum chlorideto yield polymer oils of a wide range of molecular weights andviscosities. The polybutene oils have viscosities ranging from about 40to over 3000 Saybolt Universal seconds at 210 F. corresponding tomolecular weights from about 300 to 1500. Their flash points vary fromabout 200 to 500 F. and their pour points range from 12 about ---65 F.to about 35 F. The polybutenes have the same specification tests aspetroleum oils, although they tend to have lower pour points, flashpoints and carbon residue than petroleum lubricants having an equivalentviscosity.

A variety of polymer oils, similar to the polybutenes, but utilizingother olefins of relatively low molecular weight are suitable aslubricant materials. These include polymers produced from propylenes,pentenes, hexenes, octenes. etc., or mixtures of the same. These variouspolymer oils are prepared in a manner very similar to the polybutcnesand have physical properties of a similar order.

The phosphate esters are a class of lubricant materials whose chiefbeneficial characteristic is their lack of flammability. Thesematerials, as characterized by the aryl esters of phosphoric acid, havegood lubricity or oillike properties. high film strength, resistance toheat and oxidation over a wide range of temperatures and arenon-corrosive. Typical examples of such phosphate esters are tricresylphosphate, triphenyl phosphate, trixylyl phosphate and the like.

The aromatic ethers are a class of compounds which are characterized inthat a portion of the molecule contains at least two aryl groups bridgedby an ether oxygen atom. The aromatic portion of the molecule may besubstituted by halogen or alkyl groups. In general, these compounds havea high order of thermal and oxidative stability at high temperatures.They are further very stable toward radiation and thus will find futureapplication in lubricating nuclear powered engines. Typical examples ofthese ethers are bis(methylphenoxy)benzene, bis(phenoxy)benzene,bis(chlorophenoxy)benzene, and bis(nonylphenoxy)benzene.

The following examples illustrate lubricant compositions of myinvention. Unless otherwise specified, the proportions given in theseexamples are on a weight basis.

EXAMPLE 22 One part of 10 percent di-butyl tin sulfide and 90 percent4,4 methylene bis(2,6 di-tert-butylphenol) was blended with 99 parts ofa paraflinic, mineral White oil having a sulfur content of 0.07 percent,a kinematic viscosity (ASTM D445) of 17.15 centistokes at 100 F. and3.64 centistokes at 210 F. The viscosity index of the base oil (ASTMD-567) is 107.5.

EXAMPLE 23 To 99.15 parts of a halogen-substituted polyphenylpolymethylsiloxane was added and blended 0.85 part of 25 percent dicyclohexyl tinsulfide and percent oc,a'- thiobis[2,6 di(a methylbenzyl)-p-cresol]. Thesiloxane fluid is Dow Corning F-6O fluid having a viscosity of 71centistokes at 25 C. and 24 centistokes at 75 C., a specific gravity of1.03 at 25 C., a freezing point of -70 C. and a flash point of 540 F.

EXAMPLE 24 Ten parts of 50 percent dilauryl tin sulfide and 50 percent4,4'-thiobis(2,6di-tert-butylphenol) are blended With parts of a greasecomprising 12 percent of lithium stearate, 2.5 percent of polybutene(12,000 molecular weight), 0.2 percent of 4-tert-butyl-2-phenyl phenoland 85.3 percent of di(2-ethylhexyl)adipate.

EXAMPLE 25 Five parts of 75 percent diethyl tin sulfide and 25 percent2,6-di-tert-butyl-p-cresol are blended with parts ofbis(n-dodecyl)di-n-propyl silane. Bis(n-dodecyl)di-npropyl silane has aboiling point of 208 C. at 0.50 mm. of mercury, a melting point of 5 C.and a density, d of 0.8181. Its viscosity is 14.76 centistokes at F.,3.68 centistokes at 210 F. and 1.10 centistokes at 400 F.

1 3 EXAMPLE 26 Two parts of 90 percent di-butyl tin sulfide and 10percent ethylene glycol bis(3,5 di sec-butyl-4-hydroxybenzoate) areblended with 98 parts of an aromatic ether which isbis(methylphenoxy)benzene. The bis(methylphenoxy)benzene is a mixture ofisomers in which the methyl groups are ortho, meta, or para to the etheroxygen linkage. The mixture is liquid in the temperature range from 5 to741 F. at 760 mm. pressure. Its viscosity is 550 centistokes at 32 F.,and it is thermally stable to 716 F.

EXAMPLE 27 Four parts of 1 percent diamyl tin sulfide and 99 percent2,2-methylene bis(4-methyl-6-tert-butylphenol) are blended with anLB-165 polyalkylene glycol oil. The oil has a viscosity of 165 SayboltUniversal seconds (SUS) at 100 F. and 48.6 SUS at 210 F. Its viscosityindex is 148, its ASTM pour point is -50 F., its flash point is 410 F.and its fire point is 460 F.

EXAMPLE 28 Three one-hundredths part of 30 percent diphenyl tin sulfideand 70 percent 2,6-di-tert-butyl-u-dimethylamino p-cresol are blendedwith 99.97 parts of a commercial polybutene oil. The oil has a molecularweight of approximately 330, a viscosity of 114 SUS at 100 F., and aviscosity of 40.6 SUS at 210 F. Its viscosity index is 101, its flashpoint is 230 F., and its pour point is -65 F.

EXAMPLE 29 Six parts of 15 percent isopropylphenyl tin sulfide and 85percent of 2,4,6-tri(3,5-di-tert-butyl-4-hydroxybenzyl) phenol areblended with 94 parts of a tetrahydrofuranethylene oxide copolymer oil.The oil has a tetrahydrofuranethylene oxide ratio of two to one, aSaybolt viscosity at 210 F., of 83 SUS and a Saybolt viscosity at "100F. of 462 SUS.

EXAMPLE 30 Eight parts of 45 percent dibenzyl tin sulfide and 55 percent1,3,5-tri-methyl- 2,4,6 tri(3,5-di-tert-butyl-4-hydroxybenzyl)benzeneare blended with 92 parts of a complex mineral oil base grease,comprising 13.8 parts of lithium stearate, 1.7 parts of calciumstearate, 33.8 parts of a California solvent refined paraflinic base oil(356 SUS at 100 F.), and 50.7 parts of a California solvent refinedparaffinic base oil (98 SUS at 100 F.).

EXAMPLE 31 Seven one-hundredths parts of 50 percent dibutyl tin sulfideand 50 percentpentaerythritol-tetrakis[3(3,5-ditert-butyl-4-hydroxyphenyl)propionate]are blended with 99.93 parts of tricresyl phosphate. Tricresyl phosphatehas a viscosity of 25 C. of 285 SUS, its flash point is 250 C., itsboiling range at mm. of mercury is between 275 and 290 C. and itsautoignition temperature is above 1000 C.

The synergistic stabilizers impart outstanding oxidative and thermalstability to hydrocarbon-derived lubricating oils. In order todemonstrate this property comparative tests were conducted. The testused was the Panel Coker Test. This test is described in AeronauticalStandards of the Departments of Navy and Air Force, Spec. MIL-L 7808C,dated Nov. 2, 1955. In the test, a solvent-refined neutral hydrocarbonlubricating oil is placed in a sump under a metal plate heated to 550 F.The oil is periodically splashed against the heated plate and allowed todrain back into the sump. The oil is splashed for 5 seconds and drainedfor 55 seconds. This cycle is repeated for 10 hours. Following this, themetal plate is washed with hexanes and the weight gain determined. Anygain in weight is due to thermal and oxidative breakdown of the oilleaving a carbonaceous deposit. The first series of 14 tests werecarried out employing as stabilizers di-butyl tin sulfide, 4,4-methylenebis(2,6-di-tert-butylphenol), and the combination of the two. Thedeposit weight formed is shown in the following table.

As the above data shows, 0.1 percent di-butyl tin sulfide results in adeposit of 22 mg. On increasing the amount of di-butyl tin sulfidefive-fold, to 0.5 percent, the deposit weight only decreases to 13 mg.Surprisingly, the combination of 0.1 percent of di-butyl tin sulfidewith 1 percent of 4,4'-methylene bis(2,6-di-tert-butylphenol) resultedin a deposit weight of only 4 mg. This, despite the fact that 1 percentof 4,4'-methylene bis(2,6-di-tert-butylphe- 1101) by itself gave 143 mg.of deposit.

Further tests were conducted with sulfur-bridged bisphenols. Thecombinations tested were 4,4'-thiobis(2,6-ditert-butylphenol) and4,4-thiobis(2-methyl-6-tert-butylphenol) both in combination withdi-butyl tin sulfide. The following results were obtained.

Referring to the above table, it is seen that 1 percent of4,4'-thiobis(2-methyl-6-tert-butylphenol) resulted in 16 mg. of deposit,and 0.1 percent di-butyl tin sulfide yielded 22 mg. of deposit. Thecombination of the two gives a lubricant which formed only 8 mg. ofdeposit.

Even more striking are the results obtained with 4,4'-thiobis(2,6-di-tert-butylphenol). At the 1 percent level it gives alubricating oil depositing 6 mg. However, when combined with 0.1 percentdi-butyl tin sulfide, which by itself gives a lubricating oil depositing22 mg., a highly stable oil yielding only 4 mg. of deposit is obtained.Even when the amount of 4,4'-thiobis(2,6-di-tert-butylpheno1) anddi-butyl tin sulfide is decreased 50 percent the oil still retains itsunusual stability and yields only a 4 mg. deposit. The foregoing testsdemonstrate that the synergistic stabilizing compositions of the presentinvention greatly enhance the thermal and oxidative stability of theorganic material.

What is claimed is:

1. A composition comprising a mixture of:

(A) from 1-99 weight percent of a tin compound having the formula:

wherein R and R are independently selected from the group consisting ofalkyl radicals containing 1-12 carbon atoms, cycloalkyl radicalscontaining 6-12 carbon atoms, aralkyl radicals containing 7-12 carbonatoms and aryl radicals containing 6-12 carbon atoms, and

1 5 1 (B) from 199 weight percent of a phenolic compound having theformula:

wherein R and R are radicals selected from the group consisting of alphabranched alkyl radicals containing 3-20 carbon atoms, alpha-branchedaralkyl radicals containing 8-20 carbon atoms and cycloalkyl radicalscontaining 6-20 carbon atoms, and R and R are selected from the groupconsisting of hydrogen, alkyl radicals containing 1-20 carbon atoms,cycloalkyl radicals containing 620 carbon atoms and aralkyl radicalscontaining 7-20 carbon atoms.

2. Organic material normally subject to degradation in the presence ofoxygen containing a stabilizing amount of a composition of claim 1.

3. Lubricating oil containing a stabilizing amount of a composition ofclaim 1.

4. A composition of claim 1 wherein R and R are butyl radicals.

5. Organic material normally subject to degradation in the presence ofoxygen containing a stabilizing amount of a composition of claim 4.

6. A hydrocarobn selected from the group consisting of lubricating oiland polyolefins containing a stabilizing amount of a composition ofclaim 1.

C(CHs); (CHa)3 l ()(CHUa- C(CHa)3 namely,4,4-bis(2,6-di-tert-butylphenol).

10. Rubber containing a stabilizing amount of a composition of claim 9.

11. Lubricating oil containing a stabilizing amount of a composition ofclaim 9.

References Cited UNITED STATES PATENTS 2,785,188 3/1957 Coe 25252 X2,789,103 4/1957 Weinberg et al. 26045.75 3,077,451 2/1963 Antler25246.4 3,114,713 12/1963 Coffield 252-48.2 3,156,543 11/1964 Coffieldet a1. 25252 X 3,236,772 2/1966 Younghouse et a1. 25246.4

DANIEL E. WYMAN, Primary Examiner W. H. CANNON, Assistant Examiner US.Cl. X.R.

7 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Page: no.3,550,069 Datd September 22, 1970 Inventor) James O'Neill It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

FColumn 2, line 57, that portion of the formula reading 1 should readColumn 3, line 15, "R should read R Column 5,

lines 14-15, 'penteerythriLtol-tet:reak:i.s-L%,3,5-d1-tertbutylk-hydroxyphenyl)-propiona.te7" should readpentaerythritoltetrakis ,5 di-tert butylhydroxyphenyl) -propionat 7SIGNED AM R EALED (SEAL) Edwarflll-Fletchfilr. 3. mm'.m. L 0 EHOmissionor or rams

